This invention relates to devices for improving heat transfer, and more particularly to an improved heat transfer device for removing heat generated from air cooled integrated circuit modules or other electromechanical and electronic components.
Integrated circuit modules generate heat equal to the power used to operate them and the heat flux involved is inversely proportional to their size. Thus increasingly smaller modules result in higher heat flux values. Unless the heat is effectively dissipated, the modules often will not operate as intended. Due to design improvements, integrated circuit modules use more power and have become smaller and therefore require improved heat transfer mechanisms to handle the increased heat generated over a smaller area.
Traditional air cooled heat sinks are employed in close contact with the elements they cool. The heat sinks are typically made of a conductive material such as metal, for example aluminum or copper, and have a base from which cooling structures such as pins or fins extend to conduct heat away from the module. These sinks generally utilize a virtually uniform fin thickness and size. If the cooling fins are thin, the sink has good convective heat transfer (to the surrounding air) but poor conductive transfer (to the surrounding structure). This is because thin fins allow more fins to be placed within a given width and therefore provide greater area for heat transfer to the air. If the cooling fins are thick, however, the converse is true: good conductive transfer but poor convective transfer because of reduced total heat transfer area.
As the structures extend further away from the element to be cooled, some heat is transferred to the surrounding air via convection and less heat is transferred via conduction along the fins. Since less heat needs to be conducted in these distal regions, the fins can be reconfigured to provide greater area for increased convective heat transfer. Single stage heat sinks fail to take advantage of this principle. Thus what is needed therefore is a multi-stage heat sink in which each stage balances conductive versus convective heat transfer in order to optimize total heat transport per heat sink volume.